The Validity of IQ

April 15, 2016 RyanFaulk Uncategorized 9

So what’s the point of IQ tests? Well, they can predict lots of life outcomes. Here is a table from page 65 “The Scientific American Book of the Brain”. It shows the percentages of each IQ bracket and their life outcomes.

IQ is a better predictor of job performance than lots of things. From Schmidt and Hunter, they looked at the correlation between job performance ratings given by coworkers with various metrics to figure out what best predicts subjectively assessed work performance. The best prediction was a work sample test, followed by a structured interview and IQ test:

They also did a review of job performance studies :

Tarmo Strenze reviewed a series of longitudinal studies that compared how various life factors correlated with education level, income and occupation. The average sample size for each group is 97,083, which is the largest average sample size in any psychological study I have ever seen.

In all three groups, IQ was a better predictor for education level, occupation level, and income than any other factor.

Similarly, In the paper “Intelligence and School Grades: A meta-analysis”, Bettina Roth and co did a meta-analysis of data from more than 200 samples totaling 105,185 students, and shows that IQ tests strongly correlated with grades at 0.54.

So even if you are not convinced that IQ measures “intelligence”, it obviously measures something, and this thing is of practical importance. That said, there are some reasons to believe that IQ tests measure intelligence.

IQ Probably Measures “Intelligence”

We know that IQ tests measure intelligence because IQ tests correlate with peer and self rated intelligence. For instance, in Denissen et al. 2011 489 college students were divided into 20 groups which studied together for a period of one year. At the end of this year, subjects were asked to rate how intelligent their group mates were on a 7 point scale ranging from “not intelligence” to “very intelligent”. It was found that the better a subject did on an IQ test the smarter their group mates thought they were.

Palhusand Morgan 1997 found similar results and also showed that the correlation between peer rated intelligence and IQ increased the longer the peer knew the person being tested. They had 5 group discussion sections, and in the first section, found that in the first session, intelligence ratings were almost entirely a function of how much people talked. By the Fifth session, it was almost entirely a function of the person’s IQ – so talking a lot only increases perceived “intelligence” above IQ in the short term.

Similarly,Bailey and Hatch 1979 showed that intelligence rated by people’s close friends correlated with their IQ and Bailey and Mattetal 1977 found the same was true of spouses.

A significant body of research has also shown that IQ tests predict how intelligent people rate themselves as being (Paulhus, Lysy, and Yik 1998, ,Angelo and James 1977, and Reilly and Mulhern 1995). Clearly then, the smarter a person thinks they are, and the smarter their friends think they are, the better they tend to do on IQ tests.

So in summary, IQ tests predict life outcomes better than several factors commonly recognized to predict life outcomes, such as what your parents are like and how good your grades are. And IQ predicts one’s subjective perception of a person’s intelligence the longer you interact with them.

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Emil Kirkegaard

There’s a meta-analysis of self-estimated IQ and actual IQ. Mean r = .33. So, adjust for measurement error and it will be higher, perhaps .40 or so. https://www.ncbi.nlm.nih.gov/pubmed/22181852
Andreas Egeland

Although I am somewhat perplexed that a ~.5 correlation is considered sufficient, however I do agree that IQ does measure something, and that this thing is of practical importance.

Where it all goes wrong is when you suggest IQ then measures intelligence.
The flaw in your reasoning is pretty clear. You use another metric to define what intelligence really is (self-rating is mentioned, but obviously peer-rated intelligence is a much better metric) and then compare the IQ scores with this. This is only a valid argument if you genuinely believe that peer-rated intelligence is the objectively true measure of intelligence. In reality this is but one of many inexact metrics, so, let me be clear, this only means that IQ is correlated with intelligence. They say correlation does not imply causation, but it is perhaps less well known that a correlating factor is not a deciding factor. IQ thus gives us an indication of someone’s intelligence, not a measurement thereof.

I do enjoy writing very long comments, so although I now go on to address the studies themselves, I do repeat myself quite a lot (so you might already have read all you need to know about my position).
What is most immediately obvious is that the results are trivial, when phrased differently. IQ correlates with the what people intuit as intelligence. This says very little about intelligence, but a lot about people, in particular the ones who invented the IQ tests. It is trivial that this is the case. The IQ test would not even be known as an Intelligence Quotient if it did not have anything to do with the common perception of intelligence.

The very important issue remains: Why does this mean IQ probably measures intelligence? Do you define intelligence to be the sum of all subjective experiences of intelligence? In fact, we now run into the real issue: what is intelligence? I don’t mean to be pedantic (actually, I do), but you must define intelligence for this entire piece to make any sense.
What you seem to be saying is that IQ scores can predict how you judge other people’s intelligence. So what?
I do not accept this definition of intelligence.
- Matthew Bareno
  
  Cohen scale says anything above .5 is Large.
  Iq tests have predictive validity. Other tests of intelligence are more biologically measured.
  - Andreas Egeland
    
    Predictive validity of what? Success? Health? Education?
    So that means IQ probably measures intelligence?
    There is a hidden premise here, some kind of reasoning which assumes that the predictive validity of IQ tests implies that IQ tests measure intelligence. This hidden premise is not in any way established or defended, hence I feel confident in concluding tat the article is wrong.
    - Dave Davey
      
      You’re being ridiculously obtuse. What is meant by “intelligence” colloquially aligns almost exactly with what IQ predicts- problem solving ability. Ability to perform a range of cognitive tasks is all anyone ever means by “intelligence”, and IQ tests for this by scoring a subject’s performance in solving a range of cognitive tasks.
      You are correct in saying that strongly predicting life outcomes in so many areas makes what IQ measures of practical importance, but your reluctance to admit that this is what people most often call intelligence needs to be overcome if you are going to have a well-informed opinion on the subject.
      You also seem to pretend as if “intelligence” is not a socially derived notion. I don’t know if you understand this, but language is a social tool, and definitions are defined by consensus. So I’m sorry if this article did not satisfy your personal notion of intelligence as being accurately measured by IQ. But to me, and to pretty much everyone else on earth, what is quite often meant by intelligence is abstract reasoning.
      Your objections are pedantic, and they don’t change the fact that a quotient calculated from a subject’s ability to answer cognitively demanding questions requiring purely abstract problem solving have a lot to do with success in all sorts of practical, real aspects of life. There is no reason to think that it measures anything other than a pretty ubiquitous notion of intelligence.
      - Andreas Egeland
        
        Most of your comment is poorly veiled insults. I didn’t want to mention this, but I was originally going through every point individually, and boy, do I get handed the short straw.
        
        I am being pedantic. And obtuse. Why? Well, so that you or anyone else that agrees with the reasoning of this article will actually explain their reasoning instead of vague attempts at circular reasoning and sophistry.
        
        But what is worth responding to is the quite hilarious observation that you define intelligence in terms of ability to do abstract reasoning, yet refuse to reason abstractly about the concept of intelligence.
        What I am suggesting is that the concept of intelligence is correlated with, but not identical to, the common perception of intelligence. This is doubly true for IQ tests, which are themselves tests based on the common perception of intelligence (which itself is based on the actual, objective, platonic concept of intelligence I am discussing here [which is what most people mean when they say “intelligence”]).
        
        I specifically use the term “platonic” to dismiss your platitude about language and definitions.
        But why on earth do you think it is relevant that language is socially constructed? Why do you place an equivalency between peer-rated intelligence and the concept of intelligence? Because the word “intelligence” was defined by people? Seriously?
        What about the word “Triangle”? What about “Circle”? What about “Morality”, “Money”, “Well-being” and other words that are related to (but not identical to) the concepts we discuss? Does morality depend on public opinion? How about wealth or well-being? Does the sum of the angles of a triangle depend on what most people believe is true? Or can we actually have an abstract discussion about abstract concepts without pandering to a dictionary or the crowd? (I know I said this already, but holy shit the irony is killing me.)
      - Dave Davey
        
        My claim about language doesn’t suggest that any of the concepts you’ve enumerated are relative at all. My point is only that terms, the “signs” you could say, are defined by public use, and that this is an instance where the way that article frames intelligence very closely aligns with this use. This doesn’t imply that mob mentality determines correct moral theory, or what people refer to when they talk about geometry. But I’m trying to say that an immediate, mechanistic explanation of why things like morality are not necessarily determined by social attitudes is because they are not generally used that way in language. The common use of the word morality does not entail a particular socially defined morality because consensus had determined that the word itself doesn’t.
        
        Now is this point trivial? Maybe. But that’s what I mean when I say that you’re being pedantic. If you want to talk about platitudes, then why do you want to appeal to broad, Phil101-ish notions of platonic universality when all the article is trying to do is prove that IQ refers to the same thing that most people mean by intelligence most of the time? Explicating the ultimate nature of intelligence that encompasses all instances of reference as it relates to the IQ-Test is not required to demonstrate this basic thesis.
        
        There is no vague attempt at circular reasoning or sophistry. I just question what relevance a philosophical debate about the universal definition of intelligence has here. If you want to say that IQ is closely related but not identified with the concept of intelligence (and be very passionate about it, which it seems you are) then that’s fine. But there’s really nothing in that criticism which says anything substantial about the articles content. It’s pretty banal, or at least in this context it is.
        
        Then you say they “must define intelligence” for the entire article to make sense. Any operational definition in science is only partial, especially in the social sciences. To demand that, in addition to capturing what is meant by intelligence most of the time, the author must satisfy a platonic denotation criteria is a ridiculous standard. If the word “intelligence” were substituted with “certain facets of intelligence that are most often referred to by intelligence”, would you be satisfied? That seems silly.
John Winters

https://notpoliticallycorrect.me/2017/10/04/doctors-iq-and-job-performance/ I wonder if you could read this and tell me what you think?
TheGuy

Weird how the last three categories have the highest IQ category as slightly worse than the 110-125 IQ range.